[tex]6a + 6 = 36 + 4a + 20 = > \\ 2a = 30 + 20 = > \\ a = \frac{50}{2} = > \\ a = 25 \: \: prima \: \: zi[/tex]
[tex]a + 2 = 27 \: \: a \: \: doua \: \: zi \\ a + 2 + 2 = 29 \: \: a \: \: treia \: \: \: zi \\ a = 2 + 2 + 2 = 31 \: \: a \: \: patra \: \: zi[/tex]